1. Technical Field
A composition containing nanostructures is utilized in shock absorber applications. The method of dispersing the nanostructures together with at least some preferred surfactants are identified which can disperse carbon nanotubes in petroleum liquid medium utilizing selected dispersants and mixing methods to form stable carbon nanostructure fluid dispersions.
2. Description of the Prior Art
The term “nanostructure” refers to elongated structures, tubes, particles, rods, spheres, strands, and combinations thereof having a cross section (e.g., angular fibers having edges) or diameter (e.g., rounded) less than 1 micron. The structure may be either hollow or solid. Accordingly, the term includes “nanofibrils” and “bucky tubes”. Such structures provide significant surface area when incorporated into a structure because of their size and shape. Moreover, such fibers can be made with high purity and uniformity. Preferably, the nanostructures used in the present invention has a diameter less than 1 micron, preferably less than about 0.5 micron, and even more preferably less than 0.1 micron and most preferably less than 0.05 micron. Dispersing the nanotubes into organic medium has been a serious challenge. The nanotubes tend to aggregate, form agglomerates, and separate from the dispersion. me industrial applications require a method of preparing a stable dispersion of a selected carbon nanostructure in a liquid medium.
For instance, U.S. Pat. No. 5,523,006 by Strumban teaches the user of a surfactant and an oil medium; however, the particles are Cu—Ni—Sn—Zn alloy particles with the size from 0.01 micron and the suspension is stable for a limited period of time of approximately 30 days. Moreover, the surfactants don't include the dispersants typically utilized in the lubricant industry.
U.S. Pat. No. 5,560,898 by Uchida et al. teaches that a liquid medium is an aqueous medium containing a surfactant; however, the stability of the suspension is of little consequence in that the liquid is centrifuged upon suspension.
U.S. Pat. No. 5,853,877 by Shibuta teaches dispersing disentangled nanotubes in a polar solvent and forming a coating composition with additives such as dispersing agents; however, a method of obtaining a stable dispersion is not taught.
U.S. Pat. No. 6,099,965 by Tennent et al. utilizes a kneader teaching mixing a dispersant with other reactants in a liquid medium using a high-torque dispersing tool, yet sustaining the stability of the dispersion does not appear to be taught nor suggested.
None of the conventional methods taught provide a process for dispersing and maintaining nanostructures in suspension comprising a lubricant additive for use in a shock absorber nanofluid composition as described and claimed in the instant invention.